Why do I receive 'Data type mismatch' error when using a VCO in simulink?

This is the error:

Data type mismatch. Input port 2 of '[FileName]/Frequency of single tone/Calculate single tone
frequency/Set to Zero if previous time was zero' expects a signal of data type 
'double'. However, it is driven by a signal of data type 'boolean'.

Edit: Attached the simulink model.